Photo detector consisting of tunneling field-effect transistors and the manufacturing method thereof

ABSTRACT

The present invention belongs to the technical field of optical interconnection and relates to a photo detector, in particular to a photo detector consisting of tunneling field-effect transistors.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention belongs to the technical field of opticalinterconnection and relates to a photo detector, m particular to a photodetector consisting of tunneling field-effect transistors.

2. Description of Related Art

Compared with the traditional aluminum, copper has the followingadvantages: 1, the resistivity of copper is smaller (Cu: 1.7μΩ/cm, Al:3μΩ/cm; 2, the parasitic capacitance of the copper interconnection issmaller than that of the aluminium interconnection; 3, due to lowresistance, the power consumption of the copper interconnection issmaller than that of the aluminum interconnection; 4, theelectro-migration resistance of copper is better than that of aluminum(Cu<10⁷A/cm², Al<10⁶A/cm²), connection cavities generated byelectro-migration are avoided, so that the reliability of the device isimproved. Therefore, devices adopting copper interconnections are ableto meet the requirements of high frequency, high integration, largepower, large capacitance and long service life; and the traditionalaluminum interconnection process is gradually replaced by the copperinterconnection process.

With the further development of integrated electronic device technology,the power consumption and delay of copper interconnections also hasgradually failed to meet demands, so the pursuit of technology withlower power consumption and fester interconnection is the futuredevelopment trend. Compared with copper interconnections, opticalinterconnections have the advantages of high bandwidth and low loss, andhave no problems in crosstalk, matching, and electromagneticcompatibility. The single-chip optical interconnection has been widelyapplied at present; in the future, the optical interconnection stands agood chance to replace the copper interconnection.

In the optical interconnection technology, the photo detector convertsthe optical signals and the decide signal plays the main rose. Usually,the photo detector consists of p-i-n diodes. The basic structure isshows in the FIG. 1: a blocking layer (intrinsic layer), namely i layer100 b, is added, between the p area 100 a and the n area 100 c of thecommon photoelectric diode, and light reaches the p area via ananti-reflection film 104. With a protective film 102 and electrodes 101,103, when a high reverse bias is applied to the pn node, the blockinglayer of the pn node produces photon-generated camera under the light,and the photon-generated earners are driven by the external bias todrift directionally so as to produce photo-generated current.

Due to the thick blocking layer, the node capacitance of the p-i-n diodechanges are small and the blocking electric field becomes thicker, whichenlarges the area for light absorption and light conversion, so thequantum efficiency is improved and the wavelength sensitivity isincreased at the same time. However, the thickening of the blockinglayer influences the response speed of the photo detector to a largeextent, and the p-i-n diode requires a higher bias to make lookingcollisions appear in the diode, so the power consumption is increased.

BRIEF SUMMARY OF THE INVENTION

The present invention aims to provide a photo detector with low productenergy consumption and fast response speed.

To fulfill the mentioned aim, the present invention provides a photodetector consisting of tunneling field-effect transistors. The structureof the photo detector comprises:

-   a semiconductor substrate;-   Tunneling field-effect transistor formed on the semiconductor    substrate;-   and a fiber and reflection layer formed on the tunneling    field-effect transistor.

Moreover, the tunneling field-effect transistor has a vertical channelstructure, comprising a drain region of a first doping type formedunderneath the vertical channel, a resource region of a second dopingtype formed above the vertical channel, and gate regions formed on twosides of the vertical channel.

Moreover, the angle between the reflection layer and the surface of thesemiconductor substrate is 30-60 degrees, and the light rays in thefiber are able to pass through the reflection layer and then reach thesource region of the tunneling field-effect transistor, so thephoton-generated carriers are produced.

The present invention also provides a method for manufacturing a photodetector consisting of a tunneling field-effect transistor. The methodcomprises the following steps: Provide a semiconductor substrate;

Perform ion injection to form a doped region of a first doping type inthe semiconductor substrate;

Form a hard mask layer;

Form a first photoresist layer;

Mask, expose and etch to form s vertical channel structure of a device;

Strip the first photoresist layer;

Form a first insulating film layer;

Form a first conductive film layer;

Form a second photoresist layer;

Mask, expose and etch the first conductive film layer to form a gateelectrode;

Perform ion injection to form a drain region of a second doping type;

Strip the second photoresist layer;

Etch part of the first insulating film layer and etch to remove the resthard mask;

Form a second insulating film layer and etch the second insulating filmlayer;

Form a third insulating film layer and etch the second insulating filmlayer to form a contact hole;

Form a second conductive film layer and etch the second conductive filmlayer to form an electrode;

Form a lower cladding of a fiber;

Form a core layer of the fiber;

Form an upper cladding of the fiber;

Etch the upper cladding, the core layer and the lower cladding of thefiber to form a slope of 45 degrees;

and form a reflective layer.

Furthermore, the semiconductor substrate may be single-crystallinesilicon, polycrystalline silicon or Silicon on the insulator (SOI). Thehard mask is made from silicon nitride. The first inserting film may bemade from one or mixture of several of SiO₂, HfO₂, HfSiO₂, HfSiON, SiONand Al₂O₃. The second and third insulating films are made from silicondioxide or silicon nitride. The first conductive film is made of metalssuch as TIN, TaN, RuO₂ and Ru or doped polycrystalline silicon. Thesecond conductive film is made of aluminum, tungsten, or other metalmaterials. The reflective layer is made of a metal material such asaluminum or silver. Furthermore, the first doping type is an n type, andthe second doping type is a p type. Or, the first doping is a p type,and the second doping type is an n type.

In this invention, the tunneling field-effect transistor (TFET) isintegrated with the fiber, the TFET with the vertical channel is used asthe photo detector to detect light, so the required bias is low, theenergy consumption is reduced, and the output current and thesensitivity of the photo detector are improved. Meanwhile, the inventionalso adopts an autocollimation technology to manufacture the photodetector consisting of the TFET, so the process is more stable and theproduction cost is reduced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view of the p-i-n photo detector of the prior art.

FIG. 2 is a sectional view of the photo detector in one embodimentprovided by the present invention.

FIGS. 3 to 15 are process flow for manufacturing the photo detector inthe embodiment as shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The invention is farther described in detail by combining the attacheddrawings and the embodiments. In the figure, to facilitate description,the layer thickness and region thickness are amplified, but the sizes donot represent the actual dimensions. The figures fail to reflect theactual dimensions of the device accurately, but show the mutualpositions of the regions and the structures, specifically the verticaland horizontal neighborhood of the structures.

The reference drawing provides schematic views of an ideal embodiment ofthe present invention. The embodiment of the present invention shall notbe limited to the specific shapes of the regions as shown in the figure,but shall comprise all shapes, like deviations caused by manufacturing.For example, an etched curve is usually characterized by a bend orroundness and smoothness. But in this embodiment, all curves arerepresented by rectangles. The figure is schematic and shall not beconsidered as a limit of the present invention. Meanwhile, in the belowdescription, the term “substrate” may be considered to comprise asemiconductor substrate being processed or other films prepared on thesemiconductor substrate.

FIG. 2 illustrates an embodiment of the photo detector consisting of thetunneling field-effect transistor, which is a sectional view along thelength direction of the channel of the device. As shown in FIG. 2, thephoto detector is formed on a silicon substrate 201, comprising a TFETportion, a fiber portion and a reflection layer 214. The TFET comprisesa source region 202, a drain region 207, a gate dielectric layer 205 anda gate electrode 206, and a metal electrode 210 is connected to theposition of the source region 202. The fiber comprises a lower cladding211, a core layer 212 and an upper cladding 213, 208 and 209 representinsulation dielectric layers, for example silicon diode. Light rays inthe fiber are able to reach the source region 202 of the TFET afterbeing reflected by the reflection layer 214, to produce thephoton-generated carriers. When appropriate voltage is applied to theTFET, the TFET is switched on, and then the photon-generated carriersdrift directionally to produce a photon-generated current. The gatevoltage of the TFET makes the electric field in the channel rise, so thephoton-generated carriers further perform collision ionization. Suchphenomenon amplifies the photon-generated current, therefore this kindof devices still have high optical sensitivity under the condition oflow voltage at the source region and drain region.

The photo detector consisting of the tunneling field-effect transistoris capable of being manufactured by many methods. The following is theprocess flow of one embodiment for manufacturing the photo detector asshown in FIG. 2.

First, provide a silicon substrate 201 and then perform n-type ioninjection to form an n-type doped region 202 in the silicon substrate201, as shown in FIG. 3. Second, deposit a layer of hard mask 203, forexample made from silicon nitride, deposit a photoresist layer, performmasking, exposure and development to form a required pattern, etch thehard mask 203 and the silicon substrate 201 to form a vertical channelstructure of a device, and strip the photoresist to obtain a product asshown In FIG. 4.

Third, deposit an insulating film 205, a conductive film 206 and aphotoresist layer in turn, perform masking, exposure and etching on theconductive film 200 to form a gate electrode of the device, and stripthe photoresist to obtain a product a shown in FIG. 5, wherein theinsulating film 205 is one or two layers in the silicon dioxide andhigh-k material layers, and the conductive film 206 may be the dopedpolycrystalline silicon.

Fourth, perform p-type ion injection to form a drain region 207 of thedevice, as shown in FIG. 6.

After the drain region 207 is formed, etch to remove part of theinsulating film 205 and the rest hard mask 203 to form a structure asshown in FIG. 7. FIG. 8 is a top view of the TFET portion 200 of thestructure as shown in FIG. 7.

Five, deposit an insulating film 208 which may be made from siliconnitride and etch the silicon diode film 201, as shown in FIG. 9. FIG. 10is a top view of the TFET portion 200 of the structure as shown in FIG.9.

The process for manufacturing the photo detector of the presentinvention is described on the basis of the TFET portion 200 of thestructure as shown in FIG. 3 f.

First, deposit an insulating film 209 which may be made from silicondioxide, etch the silicon dioxide film to form a contact hole, deposit aconductive film 210 which may be made of aluminum, and etch theconductive film 210 to form a metal electrode, as shown in FIG. 11.

Second, form a lower cladding 211, a core layer 212 and an uppercladding 213 of a fiber in turn, wherein the reflectivity of both theupper cladding 213 and the lower cladding 211 is smaller than that ofthe core layer 212, as shown in FIG. 12. FIG. 13 is a top view of thestructure as shown in FIG. 12;

Third, etch the upper cladding 213, the core layer 212 and the lowercladding 211 of the fiber to torn a slope of 45 degrees, deposit asilver metal and then etch the sliver layer to form a reflection layer214 of the device, as shown in FIG. 14. FIG. 15 is a top view of thestructure as shown in FIG. 14;

As mentioned above, a plurality of embodiments with great different maybe constructed, it should be noted that, except those defined in theattached claims, the present invention is not limited to the embodimentsin the description.

1-8. (canceled)
 9. The method for manufacturing a photo detector consisting of a tunneling field-effect transistor having a semiconductor substrate; a tunneling field-effect transistor formed on the semiconductor substrate and a fiber and reflection layer formed on the tunneling field-effect transistor; the tunneling field-effect transistor having a vertical channel structure, comprising a drain region of a first doping type formed underneath the vertical channel, a source region of a second doping type formed above the vertical channel, and gate regions formed on two sides of the vertical channel; and, wherein the angle between the reflection layer and the surface of the semiconductor substrate is between 30 and 60 degrees, and the light rays in the fiber are able to pass through the reflection layer and then reach the source region of the tunneling field-effect transistor, so that the photon-generated carriers are produced, comprising the following steps: providing a semiconductor substrate; performing ion injection to form a doped region of the first doping type in the semiconductor substrate; forming a hard mask layer; exposing and etching the semiconductor substrate and the hard mask layer to form the vertical channel structure; forming a first insulating film layer; forming a first conductive film layer; exposing and etching the first conductive film layer to form a gate electrode; performing ion injection to form a drain region of the second doping type; etching part of the first insulating film layer and etching to remove the remaining hard mask; forming a second insulating film layer and etching the second insulating film layer; forming a third insulating film layer and etching the second insulating film layer to form a contact hole; forming a second conductive film layer and etching the second conductive film layer to form an electrode; forming a lower cladding of a fiber; forming a core layer of the fiber; forming an upper cladding of the fiber; etching the upper cladding, the core layer and the lower cladding of the fiber to form a slope of 45 degrees; and, forming a reflective layer.
 10. A method for manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 9, wherein the second and third insulating films are made from silicon dioxide or silicon nitride; the second conductive film is made of aluminum, or tungsten; and, the reflective layer is made of aluminum or silver.
 11. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 9 wherein the semiconductor substrate may be single-crystalline silicon, polycrystalline silicon or silicon on insulator (SOI).
 12. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 9 wherein the first doping type is n type, and the second doping type is p type or, the first doping is p type, and the second doping type is n type.
 13. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 9 wherein the gate region comprises a conductive film and an insulating film separating the conductive film from the vertical channel region.
 14. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 13 wherein the conductive film is made of TiN TaN, RuO₂, Ru or doped polycrystalline silicon.
 15. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 13 wherein, the insulating film is made from one or mixture of several of SiO₂, HfO₂, HfSiO₂, HfSiON, SiON and Al₂O₃.
 16. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 9 wherein the fiber comprises a core layer and two claddings located in the upper and lower side of the core layer; and, the reflection rate of the core layer is lower than that of the claddings.
 17. A method of manufacturing a photo detector consisting of a tunneling field-effect transistor of claim 9 wherein the reflective layer is made of aluminum or silver. 